The Sunn Beta amps are liked by some, some people can't live without them, especially the preamp only version. The amp uses CMOS for distortion and JFET channel switching. You'll need a footswitch to toggle between the channels or you can play through both at the same time. There is a clone footswitch or I can post a schematic (PM me). Speakers in the combos were nothing special.
Problems: There is a rare IC that manages the channel switching logic. Hard to find if you need one. I designed a little piggyback fix it that's an issue. The biggest issue is there are many 2uF non-polar electrolytic caps in the preamp. Replace them all! The voltage regulators for the preamp run hot, could use a heatsink or mount on chassis. That's the most common failure, amp won't make a sound when they go.
The old Sunn Forum is down and I don't think it's comming back. It's a shame, there was a lot of good info there.
Problems: There is a rare IC that manages the channel switching logic. Hard to find if you need one. I designed a little piggyback fix it that's an issue. The biggest issue is there are many 2uF non-polar electrolytic caps in the preamp. Replace them all! The voltage regulators for the preamp run hot, could use a heatsink or mount on chassis. That's the most common failure, amp won't make a sound when they go.
The old Sunn Forum is down and I don't think it's comming back. It's a shame, there was a lot of good info there.